1. Field of the Invention
The present invention relates to a two-wheel drive two-wheeled vehicle, and more particularly a two-wheel drive motorcycle having a rear wheel driven by a chain or shaft mechanism and the front wheel driven by a series of shafts and gears transferring power to the front wheel from either the motorcycle transmission or the driven rear wheel. Moreover, the two-wheel drive motorcycle disclosed herein is configured so that the front wheel drive components counterbalance all steering system torque reactions and moments of inertia through placement of numerous components located on the axis of steering and symmetrically within the motorcycle front fork. The novel configuration enable the rider to maintain control of the two-wheel drive motorcycle during the high-speed, high-power rotation of the engine-powered front wheel drive.
2. Description of Related Art
As motorcycle and off-road motocross riding has gained broader appeal, the demands that riders place on their vehicles have increased dramatically. Conventional motorcycles are powered through a chain or shaft linking the engine to the rear wheel. However, motocross and motorcycle riders are now facing riding conditions and obstacles where having only rear wheel drive can lead to vehicle damage, loss of control and an unstable front wheel during cornering and off-road riding in general. For professional riders, precious race time is lost avoiding obstacles or losing traction in loose rocks, sand, dirt, mud, or ice. Traction and climbing ability are severely limited in extreme mountain conditions by only having the rear wheel provide power. Accordingly, there is a need in the industry for a two-wheel drive motorcycle that efficiently and safely transfers power from the motor through the transmission to the front wheel, that provides the rider with increased ability to safely negotiate rough terrain, and that does not detract from the aesthetic qualities, appearance or function of the motorcycle itself.
While both two-wheel drive motorcycles and two-wheel drive bicycles have been attempted in the past, the present invention relating to the two-wheel drive motorcycle offers significant technical and functional innovations previously not disclosed or anticipated. The present invention features symmetrically positioned and counterbalanced front wheel drive components relative to the axis of steering and motorcycle centerline that eliminate or minimize the torque reactions that would otherwise adversely affect motorcycle control when the front wheel is driven. Additionally, the present invention illustrates a front wheel drive for a two-wheel drive motorcycle that is completely enclosed within the motorcycle frame, head tube, and front fork in a way that reduces danger to the rider from moving parts and ensures that the motorcycle steering is unencumbered.
By comparison, previous attempts at constructing a two-wheel drive motorcycle have utilized hydraulic, hydrostatic, and variations of belt, shaft or chain drives that have numerous exposed parts. Importantly, none of the previous attempts at constructing a two-wheel drive motorcycle would result in a functional two-wheel drive motorcycle. Primarily, none of the prior attempts have taken into account that a motorcycle drive system based upon rigid shafts can spin at several thousand revolutions per minute producing torque reactions along the front fork from the spinning front wheel drive system that would result in an uncontrollable pull on the front wheel. Furthermore, previous attempts have failed to provide a motorcycle with a full rage of steering.
U.S. Pat. No. 4,702,340 shows a motorcycle with a front wheel driven by a chain supported by the motorcycle fork and handlebars powering a large chain drive gear on the front wheel. The patent is assigned to Rokon International who previously produced a similar two-wheeled vehicle capable of only low-speed rough terrain maneuvering. As shown, the front wheel drive chain would severely limit the ability to manufacture a motorcycle capable or any high speed maneuvering.
U.S. Pat. Nos. 5,014,808, 5,050,699, 5,054,572, and 5,113,964 show variations of motorcycles with a front wheel powered by a series of belts, chains, gears, or sprockets from the motor to the front fork and then to the front wheel along one side of the fork. While a motorcycle does not need the same broad range of steering that is necessary for a bicycle, the presence of a bulky drive chain on one side of the motorcycle would cause problems with both steering as well as unwanted torque reactions that would make the motorcycle potentially uncontrollable at high speeds. The exposed front wheel drive chains also pose a potential hazard to the rider.
U.S. Pat. Nos. 5,873,428 and 5,894,903, JP9156570A2, EP 0 779 205 A2, and EP 0 779 205 A3 show motorcycles with a front wheel driven by hydraulic motors or hydrostatic pressure from the engine to the front wheel. A motorcycle with a front wheel driven by a hydraulic drive system would have significantly less efficient power transfer than a rigid-shaft drive system.
GB Patent Number 1,284,821 shows a motorcycle with a front wheel driven by an extremely complex shaft and gear drive system. The motorcycle includes a radically-redesigned front end without a head tube, very large gears extending well in front of the axis of steering, and a front drive system located within one fork leg. The adverse torque reactions resulting from the unbalanced front wheel drive system and high-speed rotation of the front wheel drive would likely result in a motorcycle that is uncontrollable. This configuration of the front wheel drive would also prevent a full range of steering.
WO 93/09992 (PCT/FR92/01084) discloses a front wheel drive for a two-wheel drive motorcycle that is not counterbalanced on the axis of steering and is located in a significantly enlarged front end lacking a head tube. Such a front end would interfere with the full steering range of the motorcycle during sharp turns and make the motorcycle impossible to ride on complex terrain and potentially pose a safety risk. Additionally, while the invention discloses a drive system within both fork legs, the invention fails to disclose a counter-balanced drive system as several gears are vertically offset from each other. Further, as illustrated, the dimensions of a standard motorcycle would require that the drive gears be several inches in diameter and both the shafts and gears are inadequately supported for the enormous torque that would be transferred through such a drive system design. In short, the disclosed two wheel drive vehicle fails to adequately address the problem of torque counter balancing or provide a full range of steering.
The attempts at constructing two-wheel drive two-wheeled vehicles also include several two-wheel drive bicycle designs. Generally, two-wheel drive bicycles fall into two categories: 1) permanent designs involving drive trains attached to the frame, and 2) retrofit kits which convert existing bicycles to two-wheel drive. The main drawbacks to these systems are: 1) a modification to the standard bicycle in the form of a kit is expensive when considered as an addition to a bicycle purchase, 2) the low strength flexible shaft limits the allowable loading on the system, 3) the retro-fit kit requires considerable skill to attach and cannot be designed to optimally work with every frame design, and 4) the drive mechanisms are often large and openly exposed on the outside of the frame potentially creating additional hazards for the rider and detracting from the overall appearance of the bicycle. In short, none of the two-wheel drive bicycles discussed below could be successfully modified or adapted to produce a functional two-wheel drive motorcycle. U.S. Pat. No. 4,773,662 shows a bicycle with a front wheel driven by a chain connected to a handlebar mounted hand pedaling system. The bicycle uses arm power to drive the front wheels and is adaptable to a conventional bicycle frame.
U.S. Pat. No. 5,542,689 shows a front wheel drive system for a bicycle which can be installed on a bicycle to drive the front wheel by rocking the handlebars back and forth. As with U.S. Pat. No. 4,773,662 mentioned previously, this bicycle attempts to harness the energy of the rider's arms as an additional power source for driving the bicycle. However, a drive mechanism requiring the use of the riders arms for more than steering, balance and control of the vehicle would likely create safety problems and interfere with the bicycle's operation for both professional and recreational mountain bikers.
U.S. Pat. No. 5,052,705 describes a bicycle with power distribution from the rear wheel to the front wheel via a caliper and cable drive system. The drive system is activated by a caliper clamped on the rear wheel connected by a cable to a caliper on the front wheel. Inefficient power transfer to the front wheel due to slippage as well as torque loss in the cable would likely be a problem with this system.
U.S. Pat. No. 5,224,725 describes one permanent system that has been developed utilizing a series of chains and sprockets. This design utilizes many moving parts that would make the bicycle very awkward and difficult to maintain. The exposed chain that runs along the top tube could be hazardous to the rider and the front chain also would interfere with steering.
U.S. Pat. No. 5,324,057 describes a bicycle driven with a chain meshed with both the front and rear sprockets through a plurality of gears, pulleys and spring systems to power the front wheel.
U.S. Pat. Nos. 5,332,244, 5,253,889, 5,158,314, 5,116,070, and 4,895,385 disclose two-wheel drive bicycles including a front wheel driven by flexible cables or flexible cables in combination with chains. Other systems, such as the system produced by Turner Drive Systems of Rogers, Ark., target the market for a drive system which can be retrofit to any standard bicycle frame with modifications primarily to the gearing and chain attachments necessary to drive the front wheel. As discussed above, a cable-driven front wheel results in inefficient power transfer to the front wheel due to cable wind.
U.S. Pat. No. 5,332,244 discloses chain-sprocket arrangements, along with a flexible shaft to transmit some of the power from a rear gearbox to the front wheel. The retrofit system utilizes the inner most sprocket for the drive system, however the rider can use the other sprockets to shift gears normally. Deformation of the flexible cable, and corresponding loss of efficient power transfer from the rear wheel to the front wheel is a drawback of each of these systems when compared to the rigid shaft drive of the present invention.
U.S. Pat. No. 5,158,314 uses a complex mechanical system to power the front wheel from the powered rear wheel. A first traction chain coupled to the rear wheel and attached to the frame is connected to a series of rigid and flexible shafts which attach to a second traction chain which is mounted above and powers the front wheel. U.S. Pat. No. 4,029,332 and U.S. Pat. No. 4,474,660 also describe two-wheel drive bicycles with complex chain or belt drive and pulley systems.
Bicycle hubs utilizing roller clutch bearings are described in U.S. Pat. Nos. 5,485,905 and 5,662,197. However, neither application discloses the use of the roller clutch hub to provide power transmission advantages for the front wheel drive of a two-wheel drive bicycle nor does either utilize more than a single roller clutch within the hub for added strength and durability of the hub shell.